Liquid crystal compositions

Abstract

A liquid crystal composition which shows an antiferroelectric smectic phase in a wide temperature range including room temperatures, and allows high speed operation at a low voltage. A liquid crystal composition comprising at least one kind of compound expressed as <IMAGE> shows an antiferroelectric smectic liquid crystalline phase at room temperatures. In the above-mentioned formula, both R1 and R2 are alkyl groups, X1 is a bonding group, X2 and X3 are independently selected bonding groups, k, m and n are independently selected from 0 or the integer 1, Z is CF3 or CH3, A1 and A2 are groups independently selected from a six-membered ring optionally replaced with 0 to 2 nitrogen atoms, or a group in which 2 to 3 such six-membered rings of the same kind or different kinds are linked at the para positions directly or via one or more bonding groups, wherein one or more hydrogen atoms in one or more such rings is optionally replaced with either fluorine atom, methyl group or ethyl group.

We claim: 
     
       1. A liquid crystal composition which shows an antiferroelectric smectic liquid crystalline phase at room temperatures, wherein said composition comprises a mixture of: ##STR13## 
     
     
       2. A liquid crystal composition which shows an antiferroelectric smectic liquid crystalline phase at room temperatures, wherein said composition comprises first compounds of the formulae: ##STR14## and further comprising a second liquid crystal compound of the formula: ##STR15## 
     
     
       3. A liquid crystal composition which shows an antiferroelectric smectic liquid crystalline phase at room temperatures, wherein said composition comprises a first compound of the formula: ##STR16## further comprising a second liquid crystal compound of the formula: ##STR17## and further comprising a third liquid crystal compound of the formula: ##STR18## 
     
     
       4. A liquid crystal composition which shows an antiferroelectric smectic liquid crystalline phase at room temperatures, wherein said composition comprises first compounds of the formulae: ##STR19## further comprising a second liquid crystal compound of the formula: ##STR20## and further comprising a third liquid crystal compound of the formula: ##STR21##